Add a code of conduct

[bertrandk]

Objective: Foster an inclusive environment and lower the barrier to entry in participating to the project.

Concerns

• Some past attempts at this have either been derailed by "controversy" or been drowned in equivocations. Needless to say, we should probably avoid this. 😏
• We MUST have a contact email address.
• It'd be great if the community could be empowered to self-police (i.e. little to no formal moderation).

Prior art

• MINASWAN
  • More of a motto than a COD, per se, but likely the most effective thing I've ever seen.
• The Rust Code of Conduct
  • Simple, clear and concise
  • Amazing work by the Rust team
• Citizen Code of Conduct
  • A strong template, great definitions
• Node.js's Inclusivity Working Group
  • Early days but it's definitely a novel approach (there have been similar attempts but not quite like this, it seems)
  • We have no need for this level of formalism but their focus on specificity and actionability is worth paying attention to (see: add a code of conduct nodejs/inclusivity#22)

[winkerVSbecks]

@bertrandk Atom uses this: http://contributor-covenant.org/version/1/2/0/

[bertrandk]

Ohhh...I'll take a look. Thanks.

[vanessayuenn]

resolved by #200